Putting the card onto the battlefield is optional. When the ability resolves, you can choose not to.

6/8/2016

You only sacrifice the creature if you still control it at end of turn. If that creature has left the battlefield, even if it came back, you don’t sacrifice it. Likewise, if an opponent has gained control of it, it won’t be sacrificed and will remain on the battlefield indefinitely.

6/8/2016

Putting a card onto the battlefield is optional. When the ability resolves, you can choose not to, even if you have one in your hand.